﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
using System.Collections;
using System.Reflection;

namespace Utility
{
        public static class DataTableToolkit
        {

            /// <summary>
            /// DataTable 转换为List 集合
            /// </summary>
            /// <typeparam name="TResult">类型</typeparam>
            /// <param name="dt">DataTable</param>
            /// <returns></returns>
            public static List<TResult> ToList<TResult>(this DataTable dt) where TResult : class,new()
            {
                //创建一个属性的列表
                List<PropertyInfo> prlist = new List<PropertyInfo>();
                //获取TResult的类型实例  反射的入口
                Type t = typeof(TResult);
                //获得TResult 的所有的Public 属性 并找出TResult属性和DataTable的列名称相同的属性(PropertyInfo) 并加入到属性列表 
                Array.ForEach<PropertyInfo>(t.GetProperties(), p => { if (dt.Columns.IndexOf(p.Name) != -1) prlist.Add(p); });
                //创建返回的集合
                List<TResult> oblist = new List<TResult>();

                foreach (DataRow row in dt.Rows)
                {
                    //创建TResult的实例
                    TResult ob = new TResult();
                    //找到对应的数据  并赋值
                    prlist.ForEach(p => { if (row[p.Name] != DBNull.Value) p.SetValue(ob, row[p.Name], null); });
                    //放入到返回的集合中.
                    oblist.Add(ob);
                }
                return oblist;
            }
        

        /// <summary>
        /// 转换为一个DataTable
        /// </summary>
        /// <typeparam name="TResult"></typeparam>
        /// <param name="value"></param>
        /// <returns></returns>
        /*public static DataTable ToDataTable<TResult>(this IEnumerable<TResult> value) where TResult : class
        {
            //创建属性的集合
            List<PropertyInfo> pList = new List<PropertyInfo>();
            //获得反射的入口
            Type type = typeof(TResult);
            DataTable dt = new DataTable();
            //把所有的public属性加入到集合 并添加DataTable的列
            Array.ForEach<PropertyInfo>(type.GetProperties(), p => { pList.Add(p); dt.Columns.Add(p.Name, p.PropertyType); });
            foreach (var item in value)
            {
                //创建一个DataRow实例
                DataRow row = dt.NewRow();
                //给row 赋值
                pList.ForEach(p => row[p.Name] = p.GetValue(item, null));
                //加入到DataTable
                dt.Rows.Add(row);
            }
            return dt;
        }*/

        /// <summary>
        /// 转换为一个DataTable(MS)
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="varlist"></param>
        /// <returns></returns>
        public static DataTable ToDataTable<T>(IEnumerable<T> varlist)
        {
            DataTable dtReturn = new DataTable();

            // column names  
            PropertyInfo[] oProps = null;

            if (varlist == null) return dtReturn;

            foreach (T rec in varlist)
            {
                if (oProps == null)
                {
                    oProps = ((Type)rec.GetType()).GetProperties();
                    foreach (PropertyInfo pi in oProps)
                    {
                        Type colType = pi.PropertyType;

                        if ((colType.IsGenericType) && (colType.GetGenericTypeDefinition()
                        == typeof(Nullable<>)))
                        {
                            colType = colType.GetGenericArguments()[0];
                        }

                        dtReturn.Columns.Add(new DataColumn(pi.Name, colType));
                    }
                }

                DataRow dr = dtReturn.NewRow();

                foreach (PropertyInfo pi in oProps)
                {
                    dr[pi.Name] = pi.GetValue(rec, null) == null ? DBNull.Value : pi.GetValue
                    (rec, null);
                }

                dtReturn.Rows.Add(dr);
            }
            return dtReturn;
        }

    }

}
